JPH0371925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for bending double pipes used for automobile exhaust pipes, heat insulation pipes, etc.

(Prior art) In order to prevent the inner and outer tubes from being abnormally deformed when bending a double-layered tube, conventionally water was sealed between the inner and outer tubes as a pressure transmitter and frozen. A method for later bending (Japanese Unexamined Patent Publication No. 111526/1983),
A method of enclosing paraffin and solidifying it before bending (Japanese Unexamined Patent Publication No. 57-56116), or a method of filling with sand and then bending (Japanese Utility Model Application No. 51-126331) is known. Also, when bending an ordinary single-ply pipe, sand is used as a pressure transmitter, or ferromagnetic particles are sealed inside the pipe and magnetized to restrain the mutual movement of the particles. It is also known (Japanese Unexamined Patent Publication No. 58-70926).

(Problems to be Solved by the Invention) The method of freezing water by sealing it between the inner and outer tubes requires a freezing device and low-temperature work to maintain the frozen state. However, those using paraffin require a heating device for enclosing and discharging, and there are problems in that it is difficult to completely discharge the paraffin.

In addition, in the case where the space between the inner and outer tubes is filled with sand, the density of the sand tends to be uneven because the space is narrow, and abnormal deformation tends to occur during bending in parts with low density. For this reason, when filling the sand, it is necessary to vibrate the pipe to make it dense and uniform, which is time consuming and inefficient.

(Means for Solving the Problems) The present invention makes it possible to bend double tubes without abnormal deformation by filling and magnetizing fine ferromagnetic particles between the inner and outer tubes. In the double tube bending method, which involves enclosing a pressure transmitting body between the inner tube and the outer tube and performing the bending process, one end of the thin inner tube and the outer tube are fixed to each other, and the space between the two tubes is strengthened. It is characterized by enclosing magnetic particles, sealing the other end with an annular stopper, bending the magnetized area while magnetizing the ferromagnetic particles, and then demagnetizing them to discharge the ferromagnetic particles. .

(Function) Due to magnetization, ferromagnetic particles are concentrated almost uniformly in the magnetized area at a high density, and solidify due to the bonding force between the particles, so that they become like a thick-walled tube and cannot be bent. No abnormal bending occurs in the inner and outer tubes.

(Embodiment) The drawings are for explaining an embodiment of the present invention. In Figs. 1 and 2, a double pipe 1 is made up of a thin inner pipe 2 and an outer pipe 3, and one end of the outer pipe 3 is shown. Both pipes 2 and 3 are connected between predetermined dimensions by the inward flange 4 of
5 is fixed in a concentric manner, during which fine iron oxide particles 6 are filled in the inside of the 5, and an annular stopper 7 is provided at the other end.
is press-fitted. This fine particle has a diameter of 0.1~0.5mm
is preferred.

The processing device consists of a bending roller 10, a receiver 11, a pusher 12, and an electromagnet 13. The surfaces of the bending roller 10, receiver 11, and pusher 12 that contact the double tube are the bending rollers in 1 about 10
As shown at 4, it is an arcuate surface that coincides with the outer peripheral surface of the double pipe 1. The electromagnet 13 has a coil 16 wound around a U-shaped core 15, and has magnetic poles 17, 1.
7 to sandwich the bent part of the double tube 1, and coil 16
is applied to magnetize the ferromagnetic fine particles 6. Due to this magnetization, the fine particles 6 are bonded to each other, forming an integrated solid state as a whole.

When the double tube 1 is sandwiched between the bending roller 10 and the receiving metal 11 of this processing device, and the electromagnet 13 is energized to press the push metal 12 in the direction of arrow F, the pressing force applied to the outer tube 3 will be applied to the magnetized area. is transmitted to the inner tube 2 through a layer of fine particles 6 which have become a solid state. Therefore, the outer tube 3, the layer of fine particles 6, and the inner tube 2 are integrated like a thick-walled tube, and the inner tube 2 is pressed and deformed in the same way as the outer tube 3, and has almost the same shape. Between 5
maintain. The electromagnet 13 rotates according to the deformation of the double tube 1 so as to always magnetize the processed part.

After processing the double pipe 1 to the desired curvature, the electromagnet 1
3 is demagnetized and removed from the apparatus, and the annular stopper 7 is removed.The ferromagnetic fine particles 6 have already been unintegrated due to the demagnetization, and since their particle diameters are minute, they flow easily and fill the width of the gap 5. Although it is narrow, it can be completely drained.

Figure 3 is an example of using another device, where the ring 2
Two supports 2 rotatably supported at 0,21
The double tube 1 is placed on 2 and 23, and the center is pressed with a pusher 24 from above to bend it.The electromagnet 25 moves together with the pusher 24 so that the magnetic poles are always located on both sides of the bent part. There is.

(Effect of the invention) In the above process, the ferromagnetic fine particles filled between the inner and outer tubes are almost uniformly concentrated in the magnetized area by the magnetic poles and become highly dense, and the fine particles are bonded by magnetic coupling between the fine particles. Because of its strength, it can sufficiently transmit bending pressure and prevent abnormal deformation. Therefore, unlike when using sand, there is no need to vibrate the tube while filling it, making handling easier.

Compared to the method in which water or paraffin is injected between the inner and outer tubes and then solidified before bending, the equipment is simpler as there is no need for temperature control. can be easily done as with water. Therefore, processing can be performed more efficiently and at lower cost than the conventional double pipe bending method.

In addition, although ferromagnetic fine particles are heavy, since they are only filled between the inner and outer tubes, the weight increase is small, easy to handle during processing, and the bending resistance is small. It has the advantage of being easy to process and suitable for mass production.

Furthermore, when sealing or discharging the ferromagnetic particles, it is sufficient to simply attach and detach the annular plug, so that processing before and after bending can be performed quickly. In addition, since the inner tube and outer tube are fixed to each other at one end, there is no displacement in the length direction and radial direction of both tubes after particle discharge, and as soon as the other end is fixed, a concentric double tube is formed. can get.

[Brief explanation of drawings]

The drawings are a device for explaining an embodiment of the present invention, and FIG. 1 is a front view, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. 3 is a longitudinal sectional front view of another device. DESCRIPTION OF SYMBOLS 1...Double pipe, 5...Between, 6...Ferromagnetic fine particles, 10...Bending roller, 11, 22, 23...
... Receiving money, 12, 24... Pushing money, 13, 25...
…electromagnet.

Claims (1)

[Claims] 1 In the double tube bending method, which involves enclosing a pressure transmitting body between the inner tube and the outer tube and performing the bending process, one end of the thin-walled inner tube and outer tube are fixed to each other, and a pressure transmitting body is inserted between the two tubes. It is characterized by enclosing ferromagnetic particles, sealing the other end with an annular stopper, bending the magnetized area while magnetizing the ferromagnetic particles, and then demagnetizing them to discharge the ferromagnetic particles. Double pipe bending method.